Final answer:
An anchor entry refers to the primary event date used for planning and serves as a fixed reference point in project or event scheduling.
Step-by-step explanation:
The statement which is true regarding an anchor entry is B. It is the primary event date that you use for planning. An anchor entry in the context of project management or event planning is a fixed point that helps with the organization and scheduling of various activities or tasks. It serves as a reference point around which other activities can be scheduled. This is critical for maintaining the integrity of the overall timeline of a project or program. For example, if planning a conference, the day of the main event would be considered the anchor entry and other pre-conference meetings, setup dates, and follow-up activities would be planned around this.